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Re: Need to run CLUSTER to keep performance
- From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
- To: Rafael Martinez <r(dot)m(dot)guerrero(at)usit(dot)uio(dot)no>
- Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org
- Subject: Re: Need to run CLUSTER to keep performance
- Date: Mon, 12 Nov 2007 16:31:41 +0000
Rafael Martinez wrote:
DETAIL: 83623 dead row versions cannot be removed yet.
Looks like you have a long-running transaction in the background, so VACUUM can't remove all dead tuples. I didn't see that in the vacuum verbose outputs you sent earlier. Is there any backends in "Idle in transaction" state, if you run ps?
In 8.1, CLUSTER will remove those tuples anyway, but it's actually not correct. If the long-running transaction decides to do a select on hosts-table later on, it will see an empty table because of that. That's been fixed in 8.3, but it also means that CLUSTER might no longer help you on 8.3. VACUUM FULL is safe in that sense in 8.1 as well.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com
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